1. Field of the Invention
The present invention relates to a facsimile apparatus having an auto-receive function. The present invention also relates to an externally controllable switching power supply device and, more particularly, to a power supply device suitable for, e.g., a facsimile apparatus having a standby state.
2. Related Background Art
Conventionally, an apparatus having a standby state such as a facsimile apparatus generally adopts a switching power supply or the like as its power supply. In a standby state or during operation, the switching power supply is always enabled. Also, another apparatus has a sub power supply for a standby state in addition to a main power supply. In an apparatus of this type, only the sub power supply is enabled in the standby state, and the main power supply is enabled during only an operation, thus achieving low power consumption.
In addition, the primary side of the main power supply is directly controlled by a ringing signal from a telephone line, thus attaining power saving.
However, in an apparatus in which the primary side of the main power supply oscillates to supply some power (electric power) to its secondary side like in the above-mentioned conventional facsimile apparatus, electric power of about 10 W is consumed in a standby state, and is consumed all day long for an auto-receive function, resulting in a very large electric power loss. In addition, the power supply generates radiation noise, and adversely influences other electronic devices.
Severe limitations associated with safety standards are imposed on direct control of the primary side of the main power supply using a plurality of means, and it is difficult to attain such control in practice.
A facsimile apparatus which has a printer function as its additional function has also been developed.
In such an apparatus, as for the printer function as the additional function, since switching control between a facsimile mode and a printer mode is executed by a central control unit of the facsimile apparatus, the main power supply must be enabled upon execution of mode switching control. For this reason, the main power supply must always be enabled.